<?php
/**
 * Created by PhpStorm.
 * User: DINGHAO
 * Date: 2018/11/8
 * Time: 13:12
 */
function filter($str,$start=0,$length){
    if (mb_strlen($str, 'utf-8') >$length) {
        $str = mb_substr($str, $start, $length, 'utf-8') . '......';

    }
    return $str;
}